Experiments have been carried out to study thermal wake effects in arrays of rectangular blocks e... more Experiments have been carried out to study thermal wake effects in arrays of rectangular blocks encountered in electronic equipment. Data were obtained for a series of channel heights and flow velocities. The temperature rise due to wake effects behind a single heated module was found to be fairly independent of the channel height and the position of the heated block, for a given approach velocity. The adiabatic temperature rise data for a module due to a heated element immediately upstream of it for different inter-module spacings were found to correlate well in terms of a new parameter called the surface packing density. It was reported by the authors in an earlier paper that both the adiabatic heat transfer coefficient and pressure-drop data for regular in-line arrays correlated well in terms of a composite geometric parameter called the volume packing density. These experiments have been extended to a higher Reynolds number. Empirical correlations are presented here for friction...
A finite volume methodology was developed to predict fully developed heat transfer coefficients, ... more A finite volume methodology was developed to predict fully developed heat transfer coefficients, friction factors, and streamlines for flow in a corrugated duct. The basis of the method is an algebraic coordinate transformation which maps the complex fluid domain onto a rectangle. The method can be adopted for other convection-diffusion problems in which two boundaries of the flow domain do not lie along the coordinate lines. Representative results were found for laminar flow, uniform wall temperature, and for a range of Reynolds number, Prandtl number, corrugation angle, and dimensionless interwall spacing. As seen from the streamlines, the flow patterns are highly complex including large recirculation zones. The pressure drops and friction factor results are higher than the corresponding values for a straight duct. Finally, the performance of the corrugated duct was compared with the straight duct under three different constraints—fixed pumping power, fixed pressure drop, and fixe...
Experiments were conducted to determine heat transfer coefficient in the entrance region of regul... more Experiments were conducted to determine heat transfer coefficient in the entrance region of regular in-line arrays of rectangular blocks in forced air cooling. The module-averaged heat transfer coefficient in the entrance region is usually high and falls off to periodic fully developed values by the third or fourth row of the array. Heat transfer coefficient was found to be correlated well in terms of a composite geometric parameter called the volume packing density, Reynolds number and the non-dimensional entry length. The correlations for the fully developed regime have already been developed by the authors. With the availability of entrance correlation, the overall heat transfer can now be conveniently formulated. This will enable the development of a superior predictive model for cooling of electronic components. This is a further step to more accurate prediction of temperature of electronic circuit boards
A finite volume scheme is utilized to predict fluid flow and heat transfer characteristics in rec... more A finite volume scheme is utilized to predict fluid flow and heat transfer characteristics in rectangular and V-shaped cavities. The basis of the scheme is an algebraic coordinate transformation which maps the irregular fluid domain onto a rectangle, and also an alternative method of approximating the complex boundaries by steps. The walls of the cavities are maintained at uniform temperature, and the calculations are carried out for laminar flow and for a number of geometric and flow parameters. Representative results indicate that the overall averaged Nusselt number in each cavity is moderately related to the Prandtl number, and strongly influenced by Reynolds number and the cavity angle for the V-shaped cavity, and by Reynolds number and the aspect ratio for the rectangular cavity
Analyses have been performed to obtain momentum and thermal characteristics in microchannel heat ... more Analyses have been performed to obtain momentum and thermal characteristics in microchannel heat sinks. The applicability of existing correlations for friction factor and Nusselt number is investigated. The study revealed that existing correlations based on the analytical results can predict the heat sink performance to within the accuracy limits acceptable for use in design. A user friendly computer code has been developed as an aid in the optimum design of microchannel heat sinks. The program, using thermal resistance models, operates in two modes, In mode one, the performance capabilities, power requirements and efficiencies of an existing heat sink design are evaluated. Mode two is used as a design tool for heat sink optimization. In this mode, given the overall heat sink geometry, fluid and substrate properties, and inlet and outlet boundary conditions, the program determines the optimum channel spacing and fin thickness. Implementation of the optimization scheme is presented a...
One-dimensional compressible flow models for isothermal and adiabatic flow in microchannels are d... more One-dimensional compressible flow models for isothermal and adiabatic flow in microchannels are developed and verified by comparison with a two-dimensional approximate model and available experimental results. The one-dimensional model was found to predict the mass flow rate of helium flow through a duct measuring 1.33 {micro}m by 52.25 {micro}m by 7,500 {micro}m to within 1% of those predicted by the two-dimensional model for specified inlet and outlet conditions. The results are also in good agreement with the experimental mass flow measurements. In addition, the important quantities in microflow analysis, i.e., Reynolds, Mach, and Knudsen numbers, as well as the channel hydraulic diameter, are analyzed via a parametric study. Finally, the effect of rarefaction on drag coefficient is compared with the experimental results. The comparison showed a decrease in drag coefficient for low Reynolds number flows in microchannels.
Microwave drying is one of the most important drying methods in agriculture. The online measureme... more Microwave drying is one of the most important drying methods in agriculture. The online measurement and control of material dried, as a challenging research issue, is helping to improve the drying quality of the final product and the energy utilization efficiency of microwave dryers. In order to realize the online measurement of temperature in microwave drying, a detection strategy was based on the temperature and humidity monitoring at the air outlet of coupling hot air and microwave drying method. LabVIEW programming software was employed to collect the temperature and humidity signal value at the outlet of the dryer to estimate the drying degree of the material. According to the amount of moisture removal in real-time, the microwave input power was adjusted gradually in the microwave drying process. Taking potato as material dried, the microwave power of microwave and hot air coupling drying is monitored to realize the real-time regulation. The results showed that the total color...
Faghri et al. proposed an algebraic coordinate transformation that transforms an irregular soluti... more Faghri et al. proposed an algebraic coordinate transformation that transforms an irregular solution domain onto a rectangle. In the present work, this method is extended to axisymmetric problems by mapping an irregular cross section of the solidified zone onto concentric spheres. The calculations are performed for the Stefan number in the range of 0.03 to 0.36, and for several values of the dimensionless geometric parameter characterizing the spheroidal capsule. The results are presented in form of the solid-liquid interface shapes and the ratios of the solidification zone volume to the capsule volume.
Employing a three-dimensional finite volume scheme, the dimensionless pressure drop coefficients ... more Employing a three-dimensional finite volume scheme, the dimensionless pressure drop coefficients of fibrous filter models are determined numerically and are compared with experimental results for a range of packing density and for three different fiber arrangements. Assuming periodicity in the direction of flow, the models approximate fibers contained within a filter layer as parallel cylinders, with square cross-section, with subsequent layers rotated through 90 degrees. Results show encouraging agreement with experimental data
Nederlands tijdschrift voor geneeskunde, Jan 19, 1999
The frequency of resistance to antibiotics among community acquired pathogens and the number of d... more The frequency of resistance to antibiotics among community acquired pathogens and the number of drugs to which they are resistant are increasing world wide. Antimicrobial resistance in the Netherlands is still low. Resistance to antimicrobial drugs is clearly linked to consumption of antibiotics within and outside of the hospital. Use of antibiotics in veterinary medicine may also contribute to the occurrence of antimicrobial resistance in human pathogens. Strategies to limit the spread of resistant strains should include encouraging the judicious use of antimicrobial agents. Guidelines for antibiotic therapy should be based on results derived from well designed surveillance studies.
Chapter 2 ENTRANCE DESIGN CORRELATIONS FOR CIRCUIT BOARDS IN FORCED-AIR COOLING M. Faghri, M. Mol... more Chapter 2 ENTRANCE DESIGN CORRELATIONS FOR CIRCUIT BOARDS IN FORCED-AIR COOLING M. Faghri, M. Molki, and Y. Asako CONTENTS Introduction 47 A New Correlation for Pressure Drop 49 The Experimental Apparatus and Procedure 49 Experimental ...
Experiments have been carried out to study thermal wake effects in arrays of rectangular blocks e... more Experiments have been carried out to study thermal wake effects in arrays of rectangular blocks encountered in electronic equipment. Data were obtained for a series of channel heights and flow velocities. The temperature rise due to wake effects behind a single heated module was found to be fairly independent of the channel height and the position of the heated block, for a given approach velocity. The adiabatic temperature rise data for a module due to a heated element immediately upstream of it for different inter-module spacings were found to correlate well in terms of a new parameter called the surface packing density. It was reported by the authors in an earlier paper that both the adiabatic heat transfer coefficient and pressure-drop data for regular in-line arrays correlated well in terms of a composite geometric parameter called the volume packing density. These experiments have been extended to a higher Reynolds number. Empirical correlations are presented here for friction...
A finite volume methodology was developed to predict fully developed heat transfer coefficients, ... more A finite volume methodology was developed to predict fully developed heat transfer coefficients, friction factors, and streamlines for flow in a corrugated duct. The basis of the method is an algebraic coordinate transformation which maps the complex fluid domain onto a rectangle. The method can be adopted for other convection-diffusion problems in which two boundaries of the flow domain do not lie along the coordinate lines. Representative results were found for laminar flow, uniform wall temperature, and for a range of Reynolds number, Prandtl number, corrugation angle, and dimensionless interwall spacing. As seen from the streamlines, the flow patterns are highly complex including large recirculation zones. The pressure drops and friction factor results are higher than the corresponding values for a straight duct. Finally, the performance of the corrugated duct was compared with the straight duct under three different constraints—fixed pumping power, fixed pressure drop, and fixe...
Experiments were conducted to determine heat transfer coefficient in the entrance region of regul... more Experiments were conducted to determine heat transfer coefficient in the entrance region of regular in-line arrays of rectangular blocks in forced air cooling. The module-averaged heat transfer coefficient in the entrance region is usually high and falls off to periodic fully developed values by the third or fourth row of the array. Heat transfer coefficient was found to be correlated well in terms of a composite geometric parameter called the volume packing density, Reynolds number and the non-dimensional entry length. The correlations for the fully developed regime have already been developed by the authors. With the availability of entrance correlation, the overall heat transfer can now be conveniently formulated. This will enable the development of a superior predictive model for cooling of electronic components. This is a further step to more accurate prediction of temperature of electronic circuit boards
A finite volume scheme is utilized to predict fluid flow and heat transfer characteristics in rec... more A finite volume scheme is utilized to predict fluid flow and heat transfer characteristics in rectangular and V-shaped cavities. The basis of the scheme is an algebraic coordinate transformation which maps the irregular fluid domain onto a rectangle, and also an alternative method of approximating the complex boundaries by steps. The walls of the cavities are maintained at uniform temperature, and the calculations are carried out for laminar flow and for a number of geometric and flow parameters. Representative results indicate that the overall averaged Nusselt number in each cavity is moderately related to the Prandtl number, and strongly influenced by Reynolds number and the cavity angle for the V-shaped cavity, and by Reynolds number and the aspect ratio for the rectangular cavity
Analyses have been performed to obtain momentum and thermal characteristics in microchannel heat ... more Analyses have been performed to obtain momentum and thermal characteristics in microchannel heat sinks. The applicability of existing correlations for friction factor and Nusselt number is investigated. The study revealed that existing correlations based on the analytical results can predict the heat sink performance to within the accuracy limits acceptable for use in design. A user friendly computer code has been developed as an aid in the optimum design of microchannel heat sinks. The program, using thermal resistance models, operates in two modes, In mode one, the performance capabilities, power requirements and efficiencies of an existing heat sink design are evaluated. Mode two is used as a design tool for heat sink optimization. In this mode, given the overall heat sink geometry, fluid and substrate properties, and inlet and outlet boundary conditions, the program determines the optimum channel spacing and fin thickness. Implementation of the optimization scheme is presented a...
One-dimensional compressible flow models for isothermal and adiabatic flow in microchannels are d... more One-dimensional compressible flow models for isothermal and adiabatic flow in microchannels are developed and verified by comparison with a two-dimensional approximate model and available experimental results. The one-dimensional model was found to predict the mass flow rate of helium flow through a duct measuring 1.33 {micro}m by 52.25 {micro}m by 7,500 {micro}m to within 1% of those predicted by the two-dimensional model for specified inlet and outlet conditions. The results are also in good agreement with the experimental mass flow measurements. In addition, the important quantities in microflow analysis, i.e., Reynolds, Mach, and Knudsen numbers, as well as the channel hydraulic diameter, are analyzed via a parametric study. Finally, the effect of rarefaction on drag coefficient is compared with the experimental results. The comparison showed a decrease in drag coefficient for low Reynolds number flows in microchannels.
Microwave drying is one of the most important drying methods in agriculture. The online measureme... more Microwave drying is one of the most important drying methods in agriculture. The online measurement and control of material dried, as a challenging research issue, is helping to improve the drying quality of the final product and the energy utilization efficiency of microwave dryers. In order to realize the online measurement of temperature in microwave drying, a detection strategy was based on the temperature and humidity monitoring at the air outlet of coupling hot air and microwave drying method. LabVIEW programming software was employed to collect the temperature and humidity signal value at the outlet of the dryer to estimate the drying degree of the material. According to the amount of moisture removal in real-time, the microwave input power was adjusted gradually in the microwave drying process. Taking potato as material dried, the microwave power of microwave and hot air coupling drying is monitored to realize the real-time regulation. The results showed that the total color...
Faghri et al. proposed an algebraic coordinate transformation that transforms an irregular soluti... more Faghri et al. proposed an algebraic coordinate transformation that transforms an irregular solution domain onto a rectangle. In the present work, this method is extended to axisymmetric problems by mapping an irregular cross section of the solidified zone onto concentric spheres. The calculations are performed for the Stefan number in the range of 0.03 to 0.36, and for several values of the dimensionless geometric parameter characterizing the spheroidal capsule. The results are presented in form of the solid-liquid interface shapes and the ratios of the solidification zone volume to the capsule volume.
Employing a three-dimensional finite volume scheme, the dimensionless pressure drop coefficients ... more Employing a three-dimensional finite volume scheme, the dimensionless pressure drop coefficients of fibrous filter models are determined numerically and are compared with experimental results for a range of packing density and for three different fiber arrangements. Assuming periodicity in the direction of flow, the models approximate fibers contained within a filter layer as parallel cylinders, with square cross-section, with subsequent layers rotated through 90 degrees. Results show encouraging agreement with experimental data
Nederlands tijdschrift voor geneeskunde, Jan 19, 1999
The frequency of resistance to antibiotics among community acquired pathogens and the number of d... more The frequency of resistance to antibiotics among community acquired pathogens and the number of drugs to which they are resistant are increasing world wide. Antimicrobial resistance in the Netherlands is still low. Resistance to antimicrobial drugs is clearly linked to consumption of antibiotics within and outside of the hospital. Use of antibiotics in veterinary medicine may also contribute to the occurrence of antimicrobial resistance in human pathogens. Strategies to limit the spread of resistant strains should include encouraging the judicious use of antimicrobial agents. Guidelines for antibiotic therapy should be based on results derived from well designed surveillance studies.
Chapter 2 ENTRANCE DESIGN CORRELATIONS FOR CIRCUIT BOARDS IN FORCED-AIR COOLING M. Faghri, M. Mol... more Chapter 2 ENTRANCE DESIGN CORRELATIONS FOR CIRCUIT BOARDS IN FORCED-AIR COOLING M. Faghri, M. Molki, and Y. Asako CONTENTS Introduction 47 A New Correlation for Pressure Drop 49 The Experimental Apparatus and Procedure 49 Experimental ...
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